Radial transmission line structures are known, such as for use in linear accelerators, and are considered desirable in that they can be constructed without the need for a magnetically permeable core. One example of a radial transmission line is shown in U.S. Pat. No. 5,757,146 to Carder, having a series of stacked circular modules each comprising an asymmetric Blumlein to generate a pulse along a central beam tube of a dielectric wall accelerator. One of the disadvantages, however, of a radial transmission line is the variable impedance of the line (variation with radius) and consequent distortion and dispersion of an output pulse. In accelerators applications, variable impedance can affect beam quality and performance by preventing proper beam transport, i.e. preventing a defined time independent energy gain from being imparted to a charged particle beam traversing the electric field. One known method of producing constant impedance with radius in such radial transmission lines involves varying the axial width of the radial line in proportion to the radius. This has been performed on the RADLAC accelerator built at Sandia National Laboratory in Albuquerque, N. Mex.